Method and apparatus for machining carburetor ports



May 15, 1962 w. F. ElBl. ET AL 3,034,381

METHOD AND APPARATUS FOR MACHINING vCARBURETOR PORTS Filed Aug. 11, 1960 2 Sheets-Sheet l AT-roRNEY May 15, 1962v w. F. ElBL ET AL 3,034,381

METHOD AND APPARATUS FOR MACHINING CARBURETOR PORTS Filed Aug. 11, 1960 2 sheets-sheet 2 INVENTOR. ZI//Z/b//l f'z, By cfmes )C Greene ATTORNEY METHOD ANI) APPARATUS FOR MACHINING CARBURETOR PORTS Wiiliam Frank Ebl and .laines L. Greene, Rochester,

N Y., assigner-s to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Aug. 11, 1960, Ser. No. 43,862 3 Claims. (Cl. 7732.2)

This invention relates to a method and apparatus for accurately controlling a machining operation, and more particularly, to a method and apparatus for accurately locating .and machining carburetor ports relative to a predetermined reference position on the carburetor.

Carburetors are conventionally formed from a plurality of housings including a throttle valve housing in which an induction passage is provided and in which'a plurality of fuel and air passages are also Provided. A conventional carburetor contains a movable throttle valve within the induction passage and a throttle valve control shaft extending therethrough. Theoretically, the air and fuel passages provided in a carburetor should be located in a predetermined manner relative to position or positions of the throttle valve and relative to various operating conditions. The use of mass production techniques in the manufacture of carburetors often results in dimensional variations from carburetor to carburetor in the location of the throttle valve and throttle valve shaft relative to the machined surfaces of the throttle valve housing. In previous practice, air and fuel passage such as an idle air bypass and an idle fuel bypass, have been located with reference to one of the machine surfaces on the throttle valve housing. Thus, the accuracy of the location of such passages relative to the throttle valve has depended on production dimensional control and normal dimensional variations in production throttle valve housings.

The principal object of this invention is to provide an improved method and apparatus for accurately locating machining apparatus relative to a reference surface on a workpiece. A further object is to provide an improved method and apparatus 'for accurately locating carburetor holes relative to the throttle valve thereof. Another object is to provide apparatus adapted for mass production of carburetors which have accurate and consistent dimensional characteristics. Still another object induction passage and a control lever 20 as shown in FIGURE 2. A machining head 22 is shown adjacent the throttle housing l2 and may be connected to a machine -of any conventional design, such as a drilling machine or an electric discharging machine. A lower carriage or slide 24 having a `front portion 26 and a rear portion 28 is slidably supported on a suitable guide means in a conventional manner. Suitable motor means 3G l is drivingly connected to the slide 24 by any suitable is to provide means for accurately positioning a cari buretor throttle valve housing relative to machining apparatus so that each housing so positioned is exactly located relative to the throttle valve carried thereby regardless of dimensional variations of the parts and surfaces of the housing.

Other objects and advantages lwill become apparent by a reference to the accompanying drawing illustrating a preferred embodiment of the invention and wherein:

FIGURE l is a side elevational view of the apparatus of this invention;

FIGURE 2 is a plan view, partly in section, of the apparatus shown in FGURE 1; g

FIGURE 3 is an enlarged detail view, partly in section, of a portion of the apparatus shown in FIGURE l prior to a machining-operation; and,

FIGURE 4 is an enlarged detail view,A partly in sec- I tion, of the apparatus shown in FIGURE 1 after a 'machining operation.

Referring now to FIGURE l, a suitable frame or table 10 supports the apparatus of this invention adjacent to conventional machinery capa-ble of machining holes within a carburetor throttle valve housing 12. The throttle housings to be machined are provided with an induction passage 14, a throttle valve 16, a throttle shaft 18 vwhich extends outwardly on opposite sides of the means such as a threaded shaft 32 which is connected to a conventional ydrive nut arrangement on the rear slide portion 28. The motor means 39 is actuable through yconventional circuitry (not shown) to cause reciprocation of the slide `24. An upper carriage or slide 34 is slidably mounted on suitable guide means on the front portion 26 oi the slide 24. Suitable motor means 36 is mounted on the rear portion 28 of the lower slide and is drivingly connected to the upper slide 34 through a conventional variable speed clutch and brake 3S by shaft members 40, 42. A drive nut arrangement 44 is secured to the slide 34 and is suitably. connected to the shaft 42. A conventional clamping cylinder 46 is mounted on a bracket 4S on the rear end of the upper slide 34 and a cylinder rod Sil is provided with a carburetor clamp 52 on its outer end. The carburetor clam-ping jaw and support 52 is slidably supported by a guide 'block 54 on a guide plate 56 iixed to the bracket 4?.

A clamping bracket 5S is iixed to the front end of the upper slide 34 and spaced forwardly of the cylinder bracket 48. A throttle housing positioning and clamping plate 60 is iixed to the bracket 53 in alignment with the jaw clamp 52 and includes a guide shaft 62 adapted to be received `within the induction passage 14 of the throttle housing 12. As shown in FIGURE 4, a portion `64 of the guide shaft 62 is relieved to accommodate movement of the throttle valve lo from a closed position as shown in FIGURE 3 to the open position as shown in FIGURE 4.

The control lever 20 is attached to an actuator 66 which exerts a throttle valve closing lforce on the control lever 20 due to a weight 68 supported overa pulley means 70. Any other suitable device, such as a spring mechanism, may be utilized to provide the necessary bias on the throttle control lever 20. The other end of the throttle shaft 18 is actuably connected to a cylinder'rod 72 of an actuating cylinder 74 through any suitable coupling means 76 for a purpose to be hereinafter .described. The cylinder 74 is mounted on the bracket 58 so that the cylinder rod .72 may be actuated into engagement with the end of the throttle valve shaft 18.

A gauge bracket 78 is fixed to the support frame 16 and supports a conventional indicating gauge device ySi) having an indicating dial S2 and a movable probe 84. The indicating gauge is utilizedas a locating gauge and is hereinafter referred to as such. The probe 84 'isr adapted to extend through the bracket 58 and the guide shaft 62 into the induction passage 14 for engagement with the throttle valve 16. The locating gauge Sti is adjustably fixed to the bracket 78 for vertical and horizontal adjustment. The locating gauge includes a plurality of conventional circuit controlling contacts (not shown) which are engageable by the movable probe 84 at predetermined positions. A collecting pan 86 maybe provided beneath the valve-housing 12 to collect-dielectric fluid if an electric discharge machining process iS used. Suitable circuit controlling limit switches 88, 90 and 92 are provided to control positioning of the slide members and are actuable -by adjustable contacts 94,' 96 carried by the slide 24.

Operation coupling member 66. The operator then returns to a remote station having suitable circuit actuating means, such asa pair 'of palmbuttons (not shown) as conventionally provided as a safety measure. The operator depresses the palm buttons and a machining cycle is initiated by actuation of the clamping cylinder 46. which moves the carburetor clamp jaw S2 toward the bracket 5S. The throttle valve housing 12Y is thereby clampedV against the support plate 66 and over the guide shaft 62 in clamped position I between the bracket. SS and the clamping jaw'SZ. After the throttle housing is clamped in place, the motor means 30 is actuated to move the slide 24 forwardly toward the loca-ting gauge 80. The slide 24 advances a relatively short distance until the contact 'engages the limit switch 99 to de-energize the motor means 3l). Actuation of the limitswitch 90 causes energization of the motor 36 and engages a high speedclutch in the clutch mechanism 38 to drive the slide 34 forwardly toward the locating gauge 86 relative to the slide 24 at a high rate of speed. As the housing 12 is moved adjacent the locating gauge 80, the probe 84 extends into Vthe induction passage 14 and eventually engages the throttle valve 16. A first set of contacts in Vthe locating gauge are actuated by movement of the probe 84 due to engagement with the throttle valvel when the housing' 12 is approximately .0015 Vinch from a predetermined position relative to the machine head 22. Actuation of the first set of contacts causes the high speed clutch to be disengaged and causes a low speed Yclutch of the clutch mechanism to be engaged to drive the slide 34 forwardly at a decreased rate of speed of approximately .001 inch per second. When the carburetor body reaches the predetermined position relative` tothe machining head 22,

. a second set of contacts inthe locating gauge are actuated by the further depression of the probe 84 which is in conl tinued engagement with the throttle valve 16. Actuation of the second set of contacts disengages the low speed clutch and energizesr the brake mechanism to exactly position the valve housing 12 relative to the'machine head 22 in relation to the closed position'of the carburetor throttle 1 valve. After suitable time delay means provided in the circuitry times out, a signal isV generated to actuate the cylinder 74 and move the carburetor throttle valve 16 to an open position against the bias'of the weight 68. As r shown in VFIGURE 4, the guide shaft 62 is provided with a relieved surface 64 to accommodate opening movement of the throttle valve 16. It is necessary to move the throt- Y tle valve to an open positionto avoiddamage thereto during the machining operation. after the time delay also causesthe machining head 22 ,y vtobe actuated into cutting engagement with the carburetor body to machine a hole or holes through the carburetor v The signal generated body and into the induction-port; It is to be noted that the Vlocation of theV machined hole-or holes will be exactly Y iring between the 'siide 34 and the rear portion 2S of the slide 24.

Although the present invention is particularly advantageous in the machining of carburetors, the method and apparatus disclosed are adaptable for use with other types of workpieces which have a movable reference surface from which other portions of the workpiece are to be located. In addition, the method and apparatus disclosed are also adaptable forlocation of a variety of workpieces from a fixed reference surface in the aforedescribed manner. Therefore, obvious modifications and rearrangements of the apparatus described are intended to be included within the scope of this invention as defined by the appended claims, except insofar as limitedby the prior art.

We claim:

l. Apparatus fol-'machining a'device,`such as a carburetor or the like, having a cavity and a movable Vreference surface located therein, a control shaft connected to said movable reference surface and having portions extending outwardly from said cavity, coupling meansV fixed to said portions, a support frame, aV gauge bracket fixed to said supportfr'ame and extending upwardly therefrom, a lower slide, said lower slide being movably supported on said frame adjacent said gauge bracket being movable from a position adjacent said gauge bracket to a position spaced outwardly away therefrom, motor means to a `actuate said lower slide between said positions, an upper slide movably supported on said lower slide, drive means xably mounted on said lower slide and connected to said upper slide for sliding actuation thereof relative to said lower slide, a clamping bracket fixed to one end ofsaid upper slide, a clamping cylinder supported on said upper slide, a carburetor clamping jaw spaced from said clamping bracket and connected to said clamping cylinder for actuationY thereby between an open position and a Vclamped position whereat a carburetor is fixedly secured between said clamping bracket and said clamping jaw, a guide shaft fixed to said clamping bracket, said guide block ybeing contoured to extend within said cavity of said carburetor when said carburetor is in said clamped position, said guide shaft being spaced from said movable surface Va sufficient dis- 'tance to permit movement thereof when Vsaid carburetor is in said clamped position, control means to engage said coupling meansrofrsaid control shaft to biasfsaid movable surface to a predetermined position, locator gauge means mounted onsaid gauge bracket, a movable probe extending outwardly from said locator gauge means towards said carburetor and lbeing aligned with said cavity in said carburetor in said clamped position, said clamping bracket and said guide shaft being apertured to receive said probe therethrough, said probe being positionable within said cavity to engage said movable surface during movement of said upperrslide, a plurality ofrcontacts provided by said locator gauge means and being actuable by movement of said probe to control said drive means, machining apparatus supported adjacent said carburetor in said clamped position, andV said probe being positioned Yrelative to said machining apparatus and said movable spaced relative tothe carburetor throttle valve and to a particular position thereof in all of the carburetors produced regardless of variation in throttle valve housing dimensions and locations of relative parts. After the machining operation is completed, the machining heads 22 are retracted and the motor means 30 is actuated to rev tract the slide 24 and thereby actuate the limit switch 92.

Actuation of the limit switch 92 generates a signal which actuates the clamping cylinder46 to retract the clamping slide for sliding actuation thereof relative to said lower `surface to cause actuation of said contacts by engagement of said probe *with said movable surface to stop said drive means when `said'carburetor has reached a predetermined position relative to ksaid machining apparatus for a mashining operation thereon.

2. Apparatus for machining a device, such as a carburetor or the like, having a cavity and a movable reference surface located therein, `a control shaft connected to saidY movable reference surface and having portions extending outwardly from said cavity, a support frame, a lower slide movably supported on said frame and being slidable thereon, motor means to actuate said lower slide, an upper slide movably supported on said lower slide and being slidable relativeY thereto, drive means fixably mounted on said lower slide and connected to said upper slide, clamping means supported on said upper slide and being movable from an open carburetor-receiving position to a clamped carburetor-holding position, a locating gauge, a gauge support bracket iXably supported adjacent said upper slide, movable probe means actuably connected to said locating gauge and being aligned with a portion of said movable reference surface and extending into the path of movement of said carburetor on said upper slide, positioning means coupled to one of said portions of said control shaft to bias said movable reference surface to a predetermined position, a plurality of contacts associated with said locating gauge and being actuable by movement of said probe to control said drive means, machining apparatus supported adjacent said upper slide, and said probe being positioned relative to said machinery apparatus and to said movable surface to cause `actuation of said cont-acts by engagement of said probe with said movable surface to stop said drive means when said earbu- 6 f retor has reached a predetermined position whereat said movable reference surface in said predetermined position is spaced a predetermined distance from said machining -apparatus for a machining operation thereon.

3. The apparatus as dened in clai-m 2 and having servo-motor means connected to another of saidportions of said control shaft, and said servo-motor means being actuably connected and responsive to said locating gauge and actuable thereby by actuation of said contacts to reposition said movable surface after said carburetor has reached said predetermined position thereof to prevent interference between said movable reference surface and said machining apparatus during the machining opera-tion.

References Cited in the file of this patent UNITED STATES PATENTS 2,042,379 Barnes et al May 26, 1936 

